Pilot study of SBR biological treatment and microfiltration for reclamation and reuse of municipal wastewater

In Israel the shortage of water and concern for the quality of groundwater resources have led to an awareness that a national wastewater reclamation program must be developed. Such a program could cover a major part of the agricultural water demand and could facilitate disposal of effluents without health hazards or environmental problems. A two-stage pilot-scale system comprising secondary sequencing batch reactor (SBR) treatment and tertiary microfiltration was operated for the treatment of Beer-Sheva municipal wastewater. The self-cleaning, continuous microfiltration system comprised a filter module made up of hollow fiber microporous membranes, with a pore size distribution of less than 0.1 μm, encapsulated into a bundle. The unit, which has a nominal filtration area of 4 m², can treat 4-5 m³ of sewage per day, at a nominal rate of about 500 L/h. SBR treatment of the raw sewage produced an effluent with a biochemical oxygen demand (BOD) of <20 mg/L and total suspended solids (TSS) of <20 mg/L. Further treatment by microfiltration resulted in a BOD <5 mg/L, TSS <1 mg/L and turbidity <0.2 nephelometric turbidity units (NTU). Bacterial counts showed 6-log removal of coliforms and fecal coliforms. These results indicate that the two-stage scheme is capable of producing an effluent that meets or even surpasses the requirements for unrestricted water reuse for agriculture.